[PATCH] drm/amdgpu/userq: skip unmapped queues in amdgpu_userq_wait_for_signal

amdgpu_userq_wait_for_signal() does an unbounded dma_fence_wait() on
every queue's last_fence before eviction. A queue disabled via MODIFY
with queue_percentage == 0 is unmapped but stays in the xarray, and its
pending fence never signals because the work will not run while the
queue is unmapped. Eviction then blocks forever, hanging the task and
wedging the GPU on a forced reset.

Only wait on fences of queues that are still mapped.

Signed-off-by: Jesse Zhang <[email protected]>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_userq.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_userq.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_userq.c
index feffebb210ea..cfbfecb05768 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_userq.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_userq.c
@@ -1302,6 +1302,16 @@ amdgpu_userq_wait_for_signal(struct amdgpu_userq_mgr *uq_mgr)
 		if (!f)
 			continue;
 
+		/*
+		 * Only a mapped queue can make progress on its fences. A queue
+		 * that has been unmapped (e.g. disabled through a MODIFY with
+		 * queue_percentage == 0) will never execute its pending work,
+		 * so its last_fence would never signal. Waiting on it here would
+		 * block the eviction path forever, so skip such queues.
+		 */
+		if (queue->state != AMDGPU_USERQ_STATE_MAPPED)
+			continue;
+
 		dma_fence_wait(f, false);
 	}
 }
-- 
2.49.0